Conventionally, a reflecting plate prepared by applying a coating material excellent in light reflection property to a metallic plate and a reflecting plate prepared by laminating resin films and the like excellent in light reflection property on a metallic plate have been used, as a reflecting plate for illumination and for a liquid crystal back light. In recent years, power saving and high efficiency have been more required in fields, such as an illuminating apparatus and a liquid crystal display. In particular, needs for space saving has been enhanced in fields, such as an electrical spectacular sign and a display. However, it is hard for the above-described reflecting plates to tackle the space saving.
Thus, a resin sheet having fine bubbles, which is excellent in light reflection property, and having high molding property, has been used, as a reflecting plate and the like for illumination and for a liquid crystal backlight (for example, see Patent Literature 1).
High functionalities are required for the light-reflecting plate that is provided to the application that is exposed to the outdoor air, such as an illuminating apparatus. The high functionalities mean various characteristics that are required for plastic products, such as antifouling property, surface hardness, and weather resistance. Generally, there sufficient functionalities are obtained in many cases, by applying to a surface part of the molded product.
Hitherto, there are a lot of examples in which foamed products having high functionalities have been realized, by addition of functional additives to a surface part of a plastic foamed sheet, for the purpose of applying these functionalities. However, it is known that such addition of functional additives generally exerts a major influence on foaming property of the resin, to cause coarsening of bubble structure.
As the method of applying high functionalities without exerting a major influence on the foaming property, a method, such as coating, laminate, or the like, is widely used (for example, see Patent Literature 2). However, these methods have a problem of high-cost due to the number of steps increased
However, regarding the foamed sheet, not only fine bubbles, but also coarse bubbles of 0.5 mm or more (or a half or larger size of the sheet thickness) are likely to generate in foam formation. In particular, in a case where the thermoplastic resin is an amorphous resin, this tendency becomes remarkable. As a result, there is a problem that makes it difficult to use the foamed sheet as various kinds of molded articles including a light reflective material.